Technical Field
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a liquid crystal horizontal orientation agent, a horizontal orientation type liquid crystal composition, and a horizontal orientation type LCD device and a method of fabricating the same.
Related Art
Since the LCD device has characteristics of low driving voltage, low power consumption, light weight, and so on, the LCD device is widely used for a display device of watches, mobile phones, computers, televisions, and so on.
The LCD device is driven in a twisted nematic (TN) mode, a vertical alignment (VA) mode and an in-plane switching (IPS) mode. Properties, e.g., a refractive index, a dielectric constant, viscosity or a phase transition temperature, of the liquid crystal material are changed according to the driving mode of the LCD device. To meet the properties, the liquid crystal material includes at least two compounds. Recently, the liquid crystal material including fine particles to improve properties of the liquid crystal material is introduced. See, for example, Japanese Patent Publication No.: 2005-247921, published on May 15, 2009.
The LCD device requires an element controlling the direction of the liquid crystal molecule. Generally, an orientation layer is formed to control the direction of the liquid crystal molecule. For example, in the TN and IPS mode of the LCD device, the direction of the liquid crystal molecule is controlled in a horizontal direction with respect to a substrate by the rubbed orientation layer. On the other hand, in the VA mode of the LCD device, which does not require a rubbing process, the liquid crystal molecule is controlled in a vertical direction with respect to the substrate by the orientation layer. The term of “orientation layer” means a layer controlling an arrangement state of the liquid crystal molecule. Generally, the orientation layer is formed of a resin such as polyimide. The term of “rubbing process” means a process of rubbing the surface of the orientation layer along one direction by rotating a roller, on which clothes, e.g., rayon or cotton, with a pre-determined number of rotation and maintaining a pre-determined distance between the roller and the substrate.
However, there are various problems resulting from the forming process of the orientation layer and the rubbing process in the arrangement control of the liquid crystal molecule using the orientation layer. For example, in the forming process of the orientation layer or the rubbing process, dusts or pin-holes are generated such that the production yield is decreased or the production costs. Such problems in the large glass substrate are increased.
To control the arrangement of the liquid crystal molecule without the orientation layer, the liquid crystal composition including dendrimer as a liquid crystal orientation agent is introduced. See, for example, Japanese Patent Publication No.: 2010-170090, published Aug. 5, 2010. Since the liquid crystal molecule is oriented in a vertical direction with respect to the substrate by the liquid crystal orientation agent introduced in the above Japanese Patent Publication, the liquid crystal orientation agent is used for the VA mode LCD device.